Laboratory investigation of the association between oral lichen planus and Hashimoto's thyroiditis

Previous studies have shown some relationship between oral lichen planus (OLP) and certain systemic comorbidities. The aim of this study was to investigate laboratory parameters between cases of Hashimoto's thyroiditis (HT) concomitant with OLP and cases of HT only.

This case-control study comprised 59 HT patients with OLP and 76 without OLP, all of whom had 5 serum thyroid-related indicators, including thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb), thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4).

Compared to cases of HT only, female predominance, presence of thyroid nodules, positive TGAb, and higher FT3/FT4 ratio were mainly observed in cases of HT concomitant with OLP (all P < 0.05). Multivariate regression analysis revealed that presence of thyroid nodules (odds ratio [OR], 10.328; 95% confidence interval [CI], 2.564-41.604), positive TGAb (OR, 6.936; 95%CI, 2.024-23.765), and higher FT3/FT4 ratio (OR, 2.577; 95%CI, 1.377-4.823) were associated significantly (all P < 0.005) with higher risk of OLP occurrence in 135 HT patients. Notably, these significant associations were not found among 30 male patients but did among 105 female patients in regression analysis.

This retrospective study revealed that presence of thyroid nodule, positive TGAb, and high FT3/FT4 ratio as risk factors were significantly associated with OLP occurrence risk in female patients with HT. This suggests that female patients suffering from HT, particularly who presented with the risk factors, should be informed about the risk of OLP development and the need for oral mucosal examination to screen for lichen lesions.